Patient-centered healthcare means focusing on the factors that affect the patient’s experience in addition to their health. This metric is measured at the end of a hospital stay with the Hospital Consumer Assessment of Healthcare Providers and Systems (H-CAHPS) survey. One of the questions on this survey that historically scores as one of the lowest is related to the patient’s perception of extraneous noises around them. Other questions focus on physician-patient communication, which also indirectly relates to the acoustical environment. Over the years, these low scores brought awareness to the healthcare industry that acoustics and noise control are vitally important to the overall patient experience.
To help combat this issue, the Facility Guidelines Institute (FGI), a non-profit that sets standards for design and construction in healthcare facilities, now solely references the Sounds & Vibration Design Guidelines for Health Care Facilities as part of their FGI Guidelines. The Guidelines are far-reaching and has been adopted by code (either in full or part) in 40+ states. Updated every four years (with 2018 being the most recent version today), the Guidelines prioritize acoustics and noise control in these facilities by organizing acoustical criteria into six categories. When the acoustics team at Henderson Engineers tackles a project, they keep these six areas of concern top-of-mind.
Site Exterior Noise
Concerns related to site exterior noise include both noise transmitting into a facility as well as noise produced by the facility, creating noise pollution for neighbors. This noise can stem from mechanical equipment, like condensing units and emergency generators, as well as environmental factors, like highway traffic and nearby railways. Designing for this concern is dictated by the Exterior Site Noise Exposure Category and the requisite Outdoor/Indoor Transmission Class (OITC) rating, which establishes the building façade composition.
Unlike site exterior noise, which focuses on keeping noise out, sound isolation focuses on keeping noise contained within an interior space, so a patient is less disturbed from activity noise generated beyond their walls. During design, the acoustical consultant must first identify the composite sound transmission class (STCC) rating of the adjacent spaces, which is a metric widely used to assess the sound isolation characteristics of a wall, floor, and other building assemblies. A higher STC rating indicates a higher level of isolation. FGI lists STC ratings for numerous room-to-room adjacencies. For example, the minimum required STCC between patient rooms on the same floor is 45; however, the minimum between an operating room and an MRI scanner room is 60 to minimize sound transmission from loud equipment.
In a hospital setting, hard surfaces are often preferred because they are the easiest to clean and maintain infection control. However, hard surfaces also reflect sound which leads to excessive sound level buildup. This exacerbates issues with communication and patient comfort/sleep. To help mitigate this issue, FGI established minimum room-average sound absorption coefficients (for numerous areas of the facility. This value is calculated by averaging the absorption coefficients ( for the materials in a space as related to the total amount of surface area.
In the healthcare field, physician-patient privilege guarantees confidentiality in accordance with HIPPA standards, which means protecting patients’ private information is just as important as protecting their health. There are four main ratings used by acoustical consultants to address speech privacy in a space (e.g. Privacy Index – PI, Articulation Index – AI, Speech Intelligibility Index – SII, and Speech Privacy Class – SPC) and the Guidelines require abiding by any one of the four. Luckily, if the other acoustic categories are adhered to, speech privacy tends to comply in lockstep. Apart from this, one trusty rule of thumb that is commonly used for speech privacy in an enclosed room is if the sum of the wall STC rating and the background noise level is at least 75, then a typical minimal amount of speech privacy is achieved. For example, a patient room with an STC-45 wall assembly should have an ambient noise level of at least 30 decibels (dBA) to ensure minimum speech privacy is attained. This is where the usage of an electronic sound masking system, commonly (but mistakenly) referred to as white noise, might be beneficial to raise ambient background noise in a subtle and equalized manner so that every small spike in noise is not disturbing or noticed by others beyond the walls.
Room Noise Levels
Room noise levels refer only to the background noise level generated by HVAC equipment. It does not include any activity noise, or beeps and chirps from medical equipment. As was the case with speech privacy, room noise levels can be expressed in several different metrics, but the industry-preferred is generally Noise Criteria (NC). FGI establishes minimum criteria depending on the type of space; however typical ranges are between NC-35 to -45 (with patient rooms being NC-40, max). High noise-sensitive areas like NICU sleep areas extend down to NC-30 while inherently louder spaces like Class 3 Imaging Rooms are NC-50.
The last concern relating to acoustics and noise control in hospitals is vibration. Designing for vibration includes isolating mechanical equipment on mounts or hangers so vibrations from equipment operation are not transferred to the structure. Additionally, vibration can occur from footfall, rolling carts, and general human movement, which can be disturbing to patients, or even bothersome to doctors during surgery. In addition, a lot of medical equipment in a hospital is sensitive to a small amount of vibration that might not be necessarily noticed by a person. Therefore, portions of the building where this sensitive equipment is located may need special structural design considerations so vibrations do not exceed equipment supplier limits. FGI’s standards include maximum floor vibration peak velocity (measured in micro-inches per second) for various areas, such as patient rooms, treatment rooms, operating rooms, and administrative areas.
When it comes to acoustics in hospitals, there’s a lot to consider. Fortunately, Henderson’s acoustics team can help you drown out the confusion to ensure your facility is offering the best patient experience possible.
Although the adoption of the Guidelines is in itself voluntary, 42 states currently mandate at least some form of the Guidelines in their building codes, making the design teams responsible for good acoustics in healthcare facilities. To learn more about our FGI: Sound Vibration Guidelines For Healthcare Facilities Henderson University course and how you can earn AIA continuing education credits, click the link here.